Forage chopping cylinders heretofore have been provided with various integral cup-like knives and other structures to assist in propelling crop material that has been severed by the cylinders on around the latter to a point of discharge. However, to our knowledge, nothing has been done in this regard with respect to those choppers which use long, continuous knives twisted into generally helical configurations and approaching their cooperating shearbar at a relatively steep angle so that a scissor-like, slicing or severing action is obtained as opposed to a more blunt, impactive chop.